The present invention relates to devices and methods for the preparation and delivery of intravenous drugs.
The invention is directed to a system, which may be located adjacent a patient""s bed (or chair), for preparing and delivering an intravenous drug from a vial to the patient. The system includes a liquid inlet for connection to a liquid supply, at least (and preferably more than) one vial receptacle, and a liquid outlet for providing the intravenous drug in mixed, liquid form to the patient. Preferably, the system includes a chamber having a variable volume, and a valve mechanism, which may be actuated to control flow between the liquid outlet, the variable-volume chamber, the vial receptacle and the liquid inlet. The system induces change in the volume of the variable-volume chamber and actuates the valve mechanism, so as to introduce liquid from the liquid inlet into the vial and reconstitute or dilute the drug and so as to deliver the drug to the patient. In a preferred embodiment, the liquid inlet, the vial receptacle, the variable-volume chamber, the liquid outlet and the valve mechanism (in other words, all components that come into contact with the liquid) are located in a disposable cassette, which may be received in a control unit.
In order to ensure that a powdered drug is completely reconstituted, the system preferably includes means for changing the chamber volume and actuating the valves so as to move the liquid repeatedly between the vial and the chamber. After the drug has been reconstituted, the system may cause the drug to be further diluted by providing an additional volume of liquid to be mixed with the drug. In a preferred embodiment, the system further includes a second chamber, and the additional volume of liquid is mixed with the drug in the second chamber. This second chamber preferably has a variable-volume as well. A primary purpose of such a second chamber (the delivery chamber) is to deliver the drug to the patient in precise quantities. The primary purpose of the first chamber (the mixing chamber) is to mix and reconstitute the drugs. To accomplish these purposes, the mixing chamber preferably has a larger volume than the delivery chamber.
Both variable-volume chambers are preferably defined by a rigid wall and a flexible membrane. Preferably, a groove is defined in the rigid wall between the conduits leading into and out of the variable-volume chambers. In the mixing chamber, the groove may be made shallow adjacent the upper conduit and wide adjacent the lower conduit, in order to promote the flow of air and liquid from the top and bottom of the mixing chamber respectively.
The disposable cassette preferably has a first valve chamber defined by a first rigid wall and a first flexible membrane, and a second valve chamber defined by a second rigid wall and a second flexible membrane; and the control unit preferably has a cam, a first actuator disposed adjacent the first flexible membrane so that movement of the first actuator causes a change in pressure on the first flexible membrane, and a second actuator disposed adjacent the second flexible membrane so that movement of the second actuator causes a change in pressure on the second flexible membrane, wherein the cam and actuators are disposed with respect to each other such that, as the cam is rotated, the actuators are moved. The cam is preferably shaped so that at any time at least one actuator is urging the corresponding flexible membrane into a closed position. The valves may be located at the inlet and outlet ends of the variable-volume chamber where the flow-rate of liquid to the patient is measured, so that liquid cannot flow through the system without being measured.
The cassette also includes, in a preferred embodiment, an outlet free-flow-prevention valve which is permanently closed to prevent flow through the outlet when the cassette is removed from a control unit which actuates the valve. Preferably, the outlet free-flow-prevention valve includes a valve chamber defined by a rigid portion of the cassette and a membrane, wherein the membrane includes a folded portion that extends towards the outside of the cassette, so that when an actuator from the control unit pushes the folded portion the membrane collapses into the valve chamber so as to restrict flow therethrough. In a further preferred embodiment, the cassette includes an inlet free-flow-prevention valve which is permanently closed to prevent flow through the liquid inlet when the cassette is removed from the control unit.
In order to ensure that all of a drug is delivered to a patient, it is important that all of the drug be purged from a manifold portion of the passageways in the cassette. A preferred method of accomplishing this purging is to further provide the cassette with an air vent in fluid communication with the manifold, an inlet valve controlling flow between the mixing chamber and the manifold, and an air valve controlling flow between the air vent and the manifold. After several volumes of medication are moved from a vial through the manifold to the mixing chamber, air is urged from the vent through the manifold to force substantially all the medication from the manifold into the mixing chamber.
Although the reconstituted drug may be delivered from the vial to the patient, preferably fluid is drawn from the vial to the mixing chamber for dilution to the proper concentration. Preferably, the diluted drug is then delivered from the mixing chamber to the delivery chamber, from which the final dose of medication may be delivered to the patient. As noted above, in alternative embodiments, a separate delivery chamber is not necessary, and the mixing chamber may deliver the diluted drug directly to the patient.